Reading directions

I am new to knitting and want to knit dish cloths. I don’t understand "all in st. 3 sts.

Possibly you’re knitting more than once into a single st (e.g. k1, p1 all in one stitch). 3 sts is probably telling you the total number of sts you should have when you’ve completed the row.
I think to know for sure you would have to link to the pattern or quote the entire row and the preceeding row.

I agree, you may have left off ‘in next stitch’ or ‘in one stitch’. Sounds like you cast on 1 st, then increase by kfbf or kp1 all in the single stitch and you have 3 sts when you’re done.