Odds are that no conversion of any kind is needed. However if you have a large size difference, ie. 39/53, and slightly inboard chainline, you might have a clearance problem with the chain brushing the outer ring on the way to the inner when coming from outer cassette sprockets.
This is a common problem even if all is OK, and if you don't ride small/small anyway you won't care. If the problem involves the 2nd or 3rd outer cassette sprockets, you can usually solve it by adjusting the chainline outward 3-4mm.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.