To get your 6 year old son out of diapers you should do away with the diapers completely and also avoid using pull-ups
Even the Pull-ups feel too much like diapers and can hinder progress by giving them a comfortable "out".
Set a Timer: Have your 6 year old son sit on the toilet every 60 to 90 minutes.
Make it a non-negotiable part of the daily routine (e.g., right when he wakes up, before leaving the house, after meals, and before bed).
Ensure a Comfortable Setup: For a 6-year-old, sitting on a massive adult toilet can feel intimidating or physically uncomfortable.
Use a sturdy Toilet Step Stool so your 6 year old son can plant his feet firmly, which helps relax his muscles for bowel movements, and use a comfortable Child Toilet Seat Insert.
Use Motivation, as at age 6, your son likely has the maturity to understand "big kid" incentives.
Let him pick out his own underwear featuring his favorite characters.
Set up a Potty Training Chart where he can track his successes.
Offer an immediate, small reward for pee, and a larger reward for poop (like a small toy or extra screen time).