Hi, Carlo
I’ve never done this myself, but I’ve looked into it. The two primary options are hardware or software. The hardware is expensive to purchase, but many post-houses who have invested in it offer standards conversion as a service. If you have the time and money, you might find someone who can do this for you.
As for software, if you are willing to spend some money, Graham Nattress makes a standards conversion plug-in which many folks recommend.
https://www.nattress.com/Products/standardsconversion/standardsconversion.htm
If you are comfortable with Compressor, I think you can accomplish this by selecting Settings>Apple>Other Workflows>Advanced Format Conversions>Apple Codecs>Apple ProRes 422 for Interlaced Material (High Quality). Apply that to your clip, then in the Inspector window, select the Frame Controls icon. Turn Frame Controls ON and go down to the Retiming Control.
See the Compressor User Manual, Chapter 20, page 264 “Using Retiming Control” and then ask someone more knowledgeable than me!
Good luck.
Mike Raff
Richmond, VA