Migrating from an Intel based iMac to a M3 iMac

A Thunderbolt 3 cable will work between those two iMac’s. You can also migrate from your Time Machine backup.

Transfer to a new Mac with Migration Assistant - Apple Support

To connect USB-A devices to the new iMac, you need USB-C to USB adapters.

Please carefully follow the directions below:

When you buy a new Mac the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes  and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts. 

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue. 

Finally, never EVER use Wi-Fi when doing Setup Assistant or Migration Assistant. Why, it simply fails in most cases. Please read and follow the directions in Setup Assistant and Migration Assistant. If you do not have a Time Machine backup of the older Mac then create one! If you are not aware of Time Machine, please read Back up your Mac with Time Machine and finally if you need an External Hard Disk to use as a Time Machine External Hard Disk then many experience users on these forums prefer the OWC Mercury Elite Pro due to it's reasonable price, high level of quality and ease of use. 

Regarding the new printer, follow the steps in: Adding a printer

The fastest and most effective way to do it is to plug your Time Machine backup drive into the new machine (using a USB-A to C adapter if necessary) and use migration assistant to migrate the data from the backup drive.

Be aware that not having a backup strategy is like driving without seatbelts. You don't need it until you do and then it's too late.

There are two type of drives, those that will crash and those that have. If you value your data do enable a backup strategy.

IMHO that is a mistake, you should ALWAYS have a Time Machine backup of your old system to safeguard your data! This is simply responsible computing.

Your solution may work okay, however for some users it does not. However the Time Machine method is the quickest and most reliable.

Your computers though, you asked, I answered so lets hope your method works okay.

michaelgraham2 wrote:

Thanks, everyone.

I am getting a Thunderbolt 4 cable. As I do not have Time Machine I am just going to use Setup Assistant to transfer from my older computer to the new one.

The Thunderbolt 4 cable will work. (I find it faster than using a USB external hard drive...but an external SSD would be just as fast).

michaelgraham2 wrote:

TLastly, I am in the process of looking for an external hard drive to start doing Time Machine backups. Also, I did get a dock, so I can connect my printer and such to this computer.

Give these a look. There are excellent hard drives for TM and are reliable: OWC Mercury Elite Pro -HDD. Of course if your budget allows OWC has external SSDs which copy much quicker but cost more.

I’m curious what data you might have that’s important enough to transfer, but not important enough to back up.

They might have a clone backup (I hope) or some other system besides Time Machine. They did not say they had *no* backup.

True, but I wouldn’t put money on that…