If that's a typical single freewheel there should be 2 notches in the inner rim, which take a freewheel remover. Make sure you know how to use these because it's very easy to damage the notches (or remover or both).
However there are hubs where the freewheel in integrated with the shell rather than a separate module threaded on. I doubt yours is this type, but wouldn't rule it out, especially if the freewheel doesn't have a removal system.
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