Menards is a chain of home improvement stores located primarily in the Midwest, not a shower enclosure manufacturer. You can, however, purchase shower enclosures from a variety of manufacturers at your local Menards store.
Menards offers a variety of tub and shower enclosures for your bathroom from companies such as Peerless, Mustee, Imperial and Dreamline. However, Menards does not offer any installation services when you purchase a shower enclosure. Each product comes with installation instructions, and their website has some helpful step-by-step videos for various DIY projects, but it is up to you to install it yourself or hire a contractor.
You can browse the list of shower enclosures that Menards sells online at Menards.com, or use their handy "Store Locator" to find a store near you. When shopping for a shower enclosure, make sure to know the dimensions of the space where you plan to install the new enclosure.