What can be done to get a baby of 7 weeks that has not Poo Poo or toilet to do so?
If your baby is exclusively breastfed, he/she may not pass stools for days or even up to 2 weeks and it is not something to worry about as long as the baby is well, not vomiting and not having swollen or hard tummy.

Do not give water or anything. Baby will definitely poo. Exclusively breastfed babies rarely get constipated as breast milk is 80% water. Keep breastfeeding exclusively.