If they’re all reporting the same thing (Mass/Volume) then switching from one unit of measurement to another is a simple transformation of the actual values. There’s no reason to use a different LOINC code just for different units of measurement when the property being reported remains the same.
I’m just doing due diligence before I contact them about requesting a new code. Sometimes I find a code which they missed and they’ll add it when I provide it to them. In this case they don’t have a mapping and I’m not finding one either, so I thought I’d check on the forum in case there was a synonym I should also look under. Thanks.