Depends on donor age
One or two embryos is the right number to transfer from a typical egg donor under the age of 30.
Three embryos would be unusual but may be acceptable if the donor is older. If we have to transfer 4 embryos the donor is not an acceptable candidate to be a donor in my opinion. Hard to give numbers without knowing the donor's age, but a 75-80%+ chance of success with 2 embryos from an under 30 donor.