Welcome!
Intel iMacs were in continuous production from 2006 through 2020. Do you have any idea of its sub-model that will tell us its age?
If available, its age can help us sort through models with known issues and consider available troubleshooting methods. Most of the model information for Intel iMacs is on a sticker on the bottom of the "foot" of the stand:

For security reasons, DO NOT post the serial number. If it shows the processor type and speed, that can also help us narrow the search.
As rkaufmann87 mentions, any iMac older than 2019 will be hard to support with parts or service, but we might spot something that will at least let you get it running enough to recover data.
AJ