Exporting a Photo Library

A number of ways you can do this. The simplest is to export all the images in your old macbooks photos app to the hard drive, copy to your new mac, and import into your new mac photos.

Alternatively you can copy the whole library to your new mac, open it on there and let new mac photos upgrade the library for use there. You could then export from that and import into your system library.

Whatever you do - you need a backup strategy in place if you don't want to lose your images again in the future. Without a backup it is not a question of if you will lose them, but when.

You could connect that time machine drive to your mac and just restore the library from it. (if it is still there).

https://support.apple.com/en-gb/guide/photos/pht6d60348f/mac

Separate topic about external drives. You can't use the drive you use for time machine. But you can use pretty much any external drive with a USB 3 or faster connection. It would be better to get a drive which has nothing else on it, so you can format it to the correct format as described below.

The external storage must be formatted APFS or MacOS extended (journaled), and not be (or have been) used for time machine. It must have the 'ignore ownership" checkbox ticked. It should not be on a memory stick, SD or similar. It stands to reason that if you want any sort of reasonable performance it should be a fast drive with a fast connection.

See

https://support.apple.com/en-gb/HT201517

Hi - when you choose to restore the library, you can choose where to restore it to. Create the folder you want to put it in first. If you want to check how that works, you can try it out with a single unimportant file before trying with the library.

Hi - you don't import the library to your current one, you import the individual photos after you have exported them from photos on your old mac - and yes, it will keep all the photos you now have.

Import is a normal way to add photos to your library. Think of it as your local book library. When they "import" books (Buy new ones and bring them in) they put them on the shelves next to the existing books. They don't replace the existing books.

Or you copy your old library onto your new mac, you will have two libraries which you have to open separately (By holding down the option key when you start photos, you can select a different library to open - like visiting two book libraries next door to each other.) When you open the old library for the first time, photos will probably take some time to upgrade it. (Make sure you keep the one on your old mac at least until the upgraded one is working on your new mac). When you can open the old one, you can choose to export all the photos to your hard disk, and import them into your normal library if you want everything in one library. (Carry all the books from one library to the library next door :-) )

The only thing you need to be careful of is not to copy your old library over the top of your current one. Copy it to a different folder just to be safe (EG create a sub folder in your pictures folder for it such as <your name>/pictures/old library/

Do you know if you have photos on your old mac, or Iphoto?, and what version of MacOS is it?

Finally, yes - if you get iCloud up and running -it will sync all your photos to all your devices. From your mac to your phone and back the other way. However you will almost certainly need to pay a few dollars/pounds a month for additional storage space.

Hi - one point then. If the library has already been upgraded for Big Sur, (IE opened in Big Sur) then it might not be possible to downgrade for Catalina.

I don't know if Catalina and Big Sur have different library formats. If they don't, you'll be OK, but if not, you one be able to change from a later version to an older version.

Not a problem if the library has only been stored on the 2020 air - and not opened.

If there is a problem, then either you need to copy the library from your older mac again, OR export the photos from the library on the 2020 air.

How did you copy it from the old mac to the air?

The easiest way is to use an external drive. If you have enough iCloud space, you could use iCloud files, but that would be slow.

Or you could copy over the network using file sharing (only for copying the library from one machine to another though, not for opening it on a remote mac)

https://support.apple.com/en-gb/guide/mac-help/mh17131/mac

You're welcome. I'm glad it all worked out.