It's not on the 1099R. What did you get a 1099R for? If it is a pension then the RMD is whatever they paid you. So put the same amount as in box 1 for the RMD.
It is on form 5498 for the previous year. For example, the RMD for 2024 is given in box 12b of form 5498 for 2023, which you received from your broker in May 2024.
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