If you're interested - this is how I would have done it, assuming the data was on the same line.
Based on the following email body.

Full flow below.

Expression used in the Compose is below that would extract out your data.
trim(first(split(last(split(outputs('Html_to_text')?['body'], 'X-User-ID:')), decodeUriComponent('%0A'))))
Output of the flow run.
