How to find Z impedance if I have only S11 (db) and phase
Careful now! Whilst the previous answer is mathematically correct - what you are actually measuring is the combination of the output match (S22) of your instrument and the input match of the unit under test.
https://www.rfcafe.com/references/electrical/vswr-mismatch.htm
Mismatch uncertainty error is often overlooked by even the most experienced engineers and scientists and is why we use very expensive metrology grade connectors and cabling.