Not certain there is enough information.
The storage units are in another state and you use a motorhome to get from your tax home to the storage units.
I think it would depend on your business and why you have to use a motor home instead of a pickup or car. Ordinarily, for example if you have a storage area which is where you keep all your inventory then going from your business location to the storage area is deductible under IRC 162. Again, ordinary and necessary is key and mileage requires documentation.
https://www.irs.gov/newsroom/small-businesses-can-benefit-from-deducting-vehicle-costs-on-their-taxes
If you're trying to write off the cost of purchasing a motor home it might be a heavy lift if there is no business purpose for buying it. The IRS often frowns on purchases like this because they're easily personal instead of business. A lot of it is documentation and meticulous records!