'A lot of' and 'lots of' are followed by a noun: It costs a lot of money. He has lots of friends. A lot of people came to the party. You need lots of time to do this. 'A lot' and 'lots' stand alone. How much bread do we need? We need lots. Was your phone cheap? No, it cost a lot. 'Lots' is more informal than 'lot'.

Your question doesn't make sense. I think your asking which one to use, but not for sure.