Welcome to the forum, and sorry to read your post.
can you (or someone else) pull them from yesterday's backup? FMP doesn't have an "undelete" key.
A serious question in a teachable moment...hopefully received in the spirit intended:
If you "have no experience whatsoever in database mgt or even use"...why do you have delete authority over records that are very important?
Ask someone who knows the database and database mgmt...verify that the records are actually deleted before taking serious actions. Most problems come as side effects from the solutions to other problems.
Look into the backup together...if there isn't one, the available options shrink mighty fast.
Review account privileges with the Dbase mgmt so that you can avoid this situation occurring again.
Best of luck to you! Let us know how it works out.