And is that folder where vdisk1.img is located?

yes

Do you know how that folder got created or why it isn't named "Windows 10 VM"?

 

Maybe you just need to fix the path.

uhm, the folder was created when the VM was created.

I did just realize that the PC I am using has 4GB of ram, and it tries to start 3 vms. one has 2 GB allocated and the other 2 have 3GB allocated.

4GB isn't enough to attempt VMs. You can probably run a few dockers with that but Unraid itself needs some RAM and certain features seem to require at least 2GB for just Unraid itself.

hmm, when I had 1 VM, it worked fine. Is there a way to delete VMs?

You can disable the VM service in Settings - VM Manager and you can delete whatever files they used in the usual way.