If your 29.97 footage is b-roll and the sound doesn’t have to sync, you can use Compressor to do the frame rate conversion.
In the “Frame Controls” tab, select Rate Conversion: Best (High quality motion compensated)
Then check the box “”so source frames play at 23.98”
Render away (get a good book).
Since the source frame rate was 29.97 and you are conforming to 23.976, your footage will have a subtle so-mo effect to it. This may be good or bad depending on it’s use.