Je nach Kontext "at" oder "about", aber nicht "of".

Hättest Du auch hieran erkennen können:
Dictionary: wonder
"of" taucht dort nicht auf...

Yes, I could see there is no "to wonder of" in the dictionary, but the dictionary is sometimes incomplete.

The whole sentence was actually:
"I have written essays in regards to my education degree at university, just in case you were wondering of my level of Italian."

Which preposition would be correct in this sentence?
Are there any other mistakes in this sentence?

I have written essays regarding my (university/college) degree in education, just in case you were wondering about my level of Italian.

I might say here, depending on what exactly you're trying to say

Or maybe 'I wrote essays in Italian as part of my teaching degree, in case you were wondering how well I speak the language', again depending on what you mean.

As others have pointed out, it is not yet entirely clear what you mean to say.

"I have written essays about my education degree at university, in case you were wondering about my level of Italian."

Do you mean that your degree is in the field of education?
Or is it that you have written essays about the education you received at university? Or did you write essays about your education degree? Or is it that you wrote essays about your education or your degree while at university?

It will not be possible to say finally whether or not there are other mistakes in the sentence until these questions are clarified.