Older iMac desktop/Mac M1 Mini/Monitor question

I have an iMac built in late 2013 and still running High Sierra. Will I be able to use it as a monitor with the Mac M1 Mini which I am thinking of purchasing? If I am able to use it that is great, but if not do I need to look for a monitor with a Thunderbolt port to work with the M1 Mini or is that necessary? Thank you for your help!