Transferring a CDL license to the USA from another country.

My husband is a Canadian Citizen. I am a US citizen. We are looking to relocate to Nevada after the immigration process is complete for him to reside in the states. My hubby has a CDL and has been driving for a fuel company for about 15 years. He's been driving for over 20 years total.

We are curious as to what are the requirements to transfer his CDL or what does the whole process entail.