Converting measurements does not have to be difficult. With practice and a strategy, your intervention students can be successful with converting. Below, I show how I teach my students to convert customary measurements. Metric is slightly different (and slightly easier!).
I started doing the "5 steps" in the middle of a lesson my first year teaching and it stuck ever since. Every year, the class names it something fancy...I can't remember any of the names now. I just know it as The 5 Steps.
Hopefully, this makes sense with the example shown. Sometimes, it seems like extra work and for your advanced students, it is too much work, but my intervention students have been successful using this strategy.
Your kiddos can get some extra practice with Customary Measurement Conversion Task Cards.
I also have a Customary Measurement Intervention Pack to help your struggling mathematicians master converting customary measurements. Find it at my TpT Store.
It's a Zoo! (Converting Customary Units) has posters, lessons, and activities for converting customary units of measurements. Find it at my TpT Store.