1-3 weeks I think... Not too sure tho!!:)
Colostrum is where the pups get the bulk of their antibodies from, the milk does not come in until 3 to 4 days after whelp. After colostrum appears it can be about a week or sometimes it isn't there until right at whelp but most often comes in a day or two before whelp. You probably want to begin taking temperature now and make sure you have finished your prenatal care as well as know what is and is not normal and all of that. Pretty much a crash course in some basics and lots of information and links for you in the link below. Normal, not normal, what you need, common problems, danger signs ect.