Not sure what you're asking here, Imran. The first slash in your example is the first character, not the one you seem to be indicating. And the second "." appears right after "worksheet". Can you clarify a little further?
Ultimately, you should be able to get what you need using the Tableau FIND function which will allow you to search for a specific sub-string within a larger string. You'd have to use a combination of multiple FINDs to get what you need.
Take a look at the string functions. String Functions
Use the SPLIT function with a delimiter of / and specify token -1 to get everything after the last slash. Then you could use a similar approach to get what you need from that string with the periods.