This could just be done quite simple with nested if-statements. Try something like this:
=IF(J2=0,K2,IF(J2=0.06,L2,IF(J2=0.21,M2)))
This only works if the percentages is formatted as percentages. If they are formatted as a string value you would need to do something like this:
=IF(J2="0%",K2,IF(J2="6%",L2,IF(J2="21%",M2)))