I have no experience with sophisticated databases ("relational" and things like that).
But I have created numerous "flat-file" databases in my time.
You said above that your databases are "simple". But that's a relative term. HOW simple?
I'm going to offer some suggestions:
See if you can download and run THIS on your new Studio:
You want the latest version, 5.4.05.
(released in July 2023)
Still runs on my 2021 MacBook Pro (m1pro) running Sonoma.
I believe it also runs on my "test copy" of Sequoia (but that's running on an Intel-based 2018 Mini).
This was once a shareware app, but now has been made free (the developer retired).
It's very simple,
but works great if all you need is "flat-file" database.
WHAT YOU WOULD NEED TO DO:
You'd need to export your existing databases from Filemaker to some kind of "text file format" for "porting".
The usual way to do it with tabs or commas delimiting fields, and (usually) a carriage return to begin the next record.
I think this is called TSV (tab separated values) or CSV (comma separated values).
Then, you'd have to find out which way iData imports them.
Hmmmm....
I just opened my copy of iData, and here's the formats it says that it can import:
Once again, I suggest you download this and try it on the new Mac (it should run on the old one, too).
It may do what you need.
And...
it's FREE.