This worksheet includes many metric conversion problems for students to hone their skills. An answer key is included.
I typically assign this as homework (after lots of practice in class), and give students free access to the answer key, so they can check their progress, and revisit, if needed.
I use the "stairstep" method of metric conversion in my classroom, with great success (middle school). You'll find my stairstep handout, as well as my "how-to" video in my store.