Ritual circumcision in adult age

If a man converts to Judaism or Islam, for instance to marry a Jewish or Muslim woman, does he have to get circumcised if he isn't already? (Yes, I know that converting to Judaism may be quite complicated even without that!) Are there restrictions or preferences on the circumcision method?

I ended up writing about such a situation, but I'm unsure if there are implausible / impossible things with respect to Judaism. Feel free to correct

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