According to Lost Media (https://forums.lostmediawiki.com/thread/9294/uncle-buck-series-missing-episodes), the following episodes have been lost into history:

Nine-to-Five
Buck to School
Yes, But Will It Fly?
Fire Sale
Tia's Tutor
A Day at the Races
Bluebell Buck
In Tia We Trust
Pig-malion
Buck to the Future
Movin Out
The People's Half Court
The Music Man (unaired)
Fame (unaired)
Sixty Candles (unaired)
My Right Foot (unaired)
Danny (unaired)
The Big Picture (unaired)


The episodes that are in bold, are said to have since been found.