[Help] First-time dog owner. How much play does my puppy need?

How do I know how much play my puppy needs? I take him to the dog park for an hour about 4-5 times a week, which I thought was enough but then I took him to daycare a couple of days ago and they said he played nonstop all day. I don't really know how to play with a puppy so most of the attention he gets at home is cuddling+training. He's pretty mellow at home but he does bark at the window whenever dogs are passing by. Is he lonely? Should I be sending him to daycare regularly? He's 6mo and I don't know the breed (but here are some pictures if it helps). via /r/dogs http://ift.tt/2qFtNQC