I just transferred my visa from F (Student) to H1B like 20 days ago. Will I be considered resident alient for tax purposes?

There is no special return that needs to be filed due to the visa change from F-1 to H-1B visa. If a person changes their visa from F-1 to H-1B they may still qualify as a nonresIdent alien for tax purposes. 

Your visa does not determine your status as a resident alien or nonresident alien for income tax purposes. That is determined by whether or not you pass the Substantial Presence Test, and there are special rules for applying that test when you have been on an F visa. If you were a nonresident alien at the beginning of the year, and are now a resident alien, then you are a dual-status alien for 2023. There are special tax-filing rules for a dual-status alien. I suggest that you consult a tax professional for help.

Here are a couple of references that might help you.

Determination of whether the student is a resident or a nonresident for tax purposes

Substantial Presence Test in IRS Publication 519, U.S. Tax Guide for Aliens