Is there a way to convert a Sims 2 skin to Sims 3? Or a mod to get one working in sims 3? Thanks.

@MoonstoneWolf: good question(s)
but this forum section is for getting feedback on creations as the title suggests - if one knows what one is doing and can show something. since you seem to need guidance for being new to skin creation i think it would be better to post in another place:

for searching an existing sims 2 skin conversion for sims 3
or
a tutorial to convert skins? ask here: WCIF Section

or do you want to discuss more comprehensive HOW to convert skins - so that you are able to do it on your own? then please ask for help in the Modding Discussion => CAS Parts Section

also: yes it is generally possible to convert Sims 2 skins for Sims 3. see here the TS2 zombieskin by burntwaffles
for creating your own skins you need the Skininator its a tool to make non-default and default custom skins. fr extracting sims 2 skins you likely need to have sims 2 on your computer installed. but how to is really better asked in the modding discussion i guess