Legally, puppies need to be at least 8 weeks old and completely weaned prior to when they can be sold and leave their mothers. Puppies can be advertised for sale prior to the 8 weeks, however not sold. Nearer to 12 weeks is suggested for separating the puppie(s) from its mom.
This ad shows that the date of birth is February 26, 2024, by adding another 8 weeks to the D.O.B means the earliest legal date of sale is on Monday, April 22, 2024.
This can be seen in the Animal Health and Welfare (Sale or Supply of Pet Animals) Regulations Act of 2019 Section 3.