How to insert a different numbers of character in a part of a text?

Hello everyone,

I do not invent (or I do not know Excel well) functions that make my life easier.
It is necessary to insert the symbol "0" in a certain place of the cadastral number. The difficulty comes from the fact that the numbers are not of the same length, i.e. you need to insert a different quantity "0".
Like this:
9584/0005:12 ---> 9584/0005:0012
9552/0001:9 ---> 9552/0001:0009
6899/0002:194 ---> 6899/0002:0194

Can anyone help with formula?