You still are not being clear. I presume 3-4" is the length of the nozzle? So 3-4" in this direction-
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You need to give us the diameter in this direction-
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I imagine it is probably 3/4" or 1". We need to know the diameter of the loc line so we can tell you what size bulkhead you need. We need to know what size bulkhead you need in order to tell you what size hole to drill.
How large is the tank? What pump are you using for the return? What size is your return piping?
Edit-
I just realized, you probably mean 3-4" is 3/4" rather than 3 to 4 inches. How large is this tank? A 3/4" loc line will not flow much water. If the tank has any size to it you'll want a bigger return.