Use a simple VLOOKUP() function like:
=VLOOKUP(E2,$A$2:$B$6,2,FALSE)
You can also use index match in this way:
=INDEX($B$2:$B$6,MATCH(E2,$A$2:$A$6,0))
With Microsoft Excel 365 you can use the below formulas:
=XLOOKUP(E2,$A$2:$A$6,$B$2:$B$6)
=@FILTER($B$2:$B$6,$A$2:$A$6=E2)