[V8889] First time sewing with a store bought pattern, Sewing Machines Parts and Sales in Los Angeles

Ok I’ve got the vogue men’s wear dress shirt pattern I listed above I picked up the larger one (mxx) but I cannot figure out what the size is supposed to be finished for the shirt mostly I don’t know how to figure out what size my husband needs his bought shirts just say 18(I think this is neck) and 34/35(arm?) Do I have the wrong pattern size do I need to alter this? Also is there any correlation chart so I can figure out what the normal measurements of men’s dress shirts are and then adjust the pattern from there?