Google My Business Guide
Website URL in Your GMB Profile
Where you link your listing to will depend on how many locations you have. We recommend that you link to your homepage if your business has 3 or less locations. Be sure that you equip your homepage with content that relates to your primary category, top keywords, and business. This can make a huge difference in your ability to rank in the local pack. If your business has more than 4 locations, then you should consider creating individual location landing pages.
Don’t forget to add tracking