OK, in what context? There are a couple of ways to get the implied lookup. Even that bit about getting the dashes to come back as slashes is easy. BUT that last part about leading zeros is going to be a lot tougher. Not impossible, though.
You want to run a query? You can't be doing that in isolation, so tell us about how you want this presented. At least two different possible scenarios come to mind and I would rather not confuse you by giving you the wrong one.
As to the dashes-to-slashes, there is a function called REPLACE that will do that in a single call.
Office VBA reference topic
docs.microsoft.com
That bit about removing a leading zero from a specific field is going to require a user-defined function, or UDF. But as a matter of fact, from what data you presented to us, a single UDF could do ALL of that WITHOUT a table. If the "required name" is always going to match the beginning of the "original name" then it would not be hard to do what you wanted with a single UDF. But again, rather than mislead you, I have to ask: Would ever occur that the original name would be
B-GA-C3a-04-0001.jpg and the required name would NOT be
B/GA/C3a/4?
My question about original/required names is to determine whether a single UDF could do everything or whether more complexity is required.