Suggested Strings for MD
Instruments- discuss specific features, luthiers, instrument problems & questions
Go to www.strothers.com and enter your VSL -- the distance between nut and bridge. Then enter the basic tuning that you are using -- DAA or DAd (not DAD or you'll get the wrong string size) one at a time -- and the calculator will do all the work for you.
Brand is irrelevant -- there are a literal handful of companies in the world which make music wire of various gauges, and they sell boxcar loads of the stuff to Martin, D'Addario, D'Arco and other string "manufacturers" who put on the ends (ball or loop), cut the string to various lengths, and put them in packages. It's all the same wire, regardless of the name on the package.
Personally I buy strings from www.juststrings.com because I can buy sets of strings for under $3 per set instead of the $5 to $8 you pay for brand name strings from a music shop.
When it comes time to replace the strings, only remove and change one string at a time. If you remove them all, you stand a chance of moving the location of the bridge, which can really mess up how your dulcimer sounds...