RegEx to replace prefix and postfix

I would like to build a RegEx expression to replace the prefix and postfix of a string. the general string is built from

1. a known prefix string


2. some letter a-z or A-Z


3. some unknown string with letters, hyphens, backslash, slash and numbers.


4. a hyphen


5. an integer number


6. the symbols #.


7. some string of letters

Examples:

KnownStringr/df-2e\d-3724#.Gkjsu
KnownStringEd\e4v-bn-824#.YKfg
KnownStringa-YK224E\yy-379924#.awws

I would like to replace the prefix and postfix of the NUMBER so that I get:

MyPrefix3724MyPostfix
MyPrefix824MyPostfix
MyPrefix379924MyPostfix