Surface tension is the to force per unit length. That means formula for surface tension is = force/length . As we know that the dimensional formula for length is L . And that for force is MLT^-2.

Unit -N/M

Dimensional formula-MLT^-2/L

So it will be ML^0T^-2

Unit -N/M

Dimensional formula-MLT^-2/L

So it will be ML^0T^-2