File folder with question mark

Do you have an alternative macOS on an external Hard Drive or USB Flash Drive that you can start up from?

You photos could be on iCloud. Failing that if you boot off another drive and it can see your internal Hard Drive you can try and copy the photos over somewhere safe. If the drive has failed, is failing, then you Amy have lost them.

Peter

A folder with a quesstion mark on boot means your Mac can't find a system folder to boot from.

Try this ...

Startup your Mac while holding down the Option key. From there you should see the Startup Manager window where you can select the startup disk then click Restart.

More help here > If a flashing question mark appears when you start your Mac - Apple Support

You need either a spare empty USB Hard Drive or USB Flash Drive over 8Gb in size.

Reformat it in Disk Utility:

Select the drive to reformat > Erase > Give it a Name > Format: Mac OS Extended (Journaled) > Scheme GUID Partition Map

Then whilst you are connected to the internet:

Open Terminal > paste in the Sierra script (at the prompt) from the following link > hit return and let it do its stuff.

How to create a bootable installer for macOS - Apple Support

It will take a while whilst it downloads and installs the Installer System on your external drive.

When it is installed, plug your drive into the iMac and restart holding down the option key and selecting the external Drive (you gave it a name).

How to select a different startup disk - Apple Support

Hopefully you will see the iMac mounted and the hard drive on it. If not we'll take it another step.

Peter

You don't go that far unless you want to.

First step is to get the iMac to boot.

You can turn the external drive into a Boot Drive, by installing the system on itself*, which will run the iMac instead of its internal Hard Drive which may be having problems.

Peter

* Which is why you want a larger Flash Drive if you are using that. I suggest at least 16Gb but 32 or 64Gb would be better and gives you room to copy material over from your other drive.

We can not see what you are looking at, you have to tell us as much as you can or we are working totally blind.

We'll take it that it is some 2102 iMac (fingers crossed) which means you should be able to install macOS High Sierra although I would recommend macOS Sierra as it is more solid and less problems.

Do you have access to a working Mac?

Peter

Do you want help with this?

It is not hard, just takes some time.

Start with what model Mac are you talking about and can you remember what version of macOS was on it?

Peter