The website mentioned above will work you through it just fine. Just make sure you have the names of the meds taken, the strengths, the frequency (usage). Also, if a brand med is taken, find out if a generic can be prescribed by the doctor (the site will tell you if one is available). It is a fairly easy site to work through, just make sure you have those items on hand before you try to work through it. And take your time.
Also, as mentioned, when you think you have narrowed it down to a few plans/companies, call them to verify. Also I would recommend applying though the company website rather than the Medicare site, JMO.
Just as an example, with my MIL back late last year, her meds were running her about $1,800 per year, one brand, two generics. Using that site, the site said a generic was available for the one brand. If she could not get the generic, total costs, meds and plan premium, would have been about $900. If all were able to be generic, about $230 per year, all premium, no med costs at all. I told her to check with her doc, he said generic is fine. So her annual costs went from $1,800 to $230. Four months into the plan, she loves it. Premium is deducted from her SS check, meds are zero cost.
Everybody is different, various areas in the country are different. Using that site is almost mandatory to get the correct plan.
(not to be considered insurance advice)