Bulk Rename Utility

Hello, I've been going through peoples replies here and trying to understand how to use the regex function but it's alluding me so far

I'm trying to rename some files in the below format - I'm sure the RegEx can do it I'm just not sure how;

01x01.EpisodeNameETC

And I want to get it into a showname s01 format so for example

The.ShowName.S01E01.EpisodeNameETC

Perhaps Prefixing the showname is easier but the part im struggling with is renaming 01x01 to S01E01?

Any help is much appreciated Thanks!