When sending greetings to Prophet Muhammad,
• some say: Peace be upon him (PBUH)
• others say: Peace be upon him and his family (S)
• some others say are more generous and say: Peace be upon him and his family (Aalihi) and his wives (wa Azwajihi) and all his companions (wa Sahbihi Ajma’een).
"May Allāh honor him and grant him peace.": (صلى الله عليه وسلم)
"peace be upon him" may be used instead of this expression "May Allah grant peace and honor on him and his family."
praise and greeting to God, Muhammad and his descendants, prayers
O Allah, send blessings upon Muhammad and the family of Muhammad)
(blessings and peace of Allah be upon him)
O Allaah, send blessings upon Muhammad and upon the family of Muhammad as You sent blessings upon Ibraaheem and upon the family of Ibraaheem; You are indeed Worthy of Praise, Full of Glory).”
References as follows:
https://islamqa.info/en/219312
https://www.al-islam.org/shiite-encyclopedia-ahlul-bayt-dilp-team/how-send-greetings-prophet-muhammad
https://en.wikipedia.org/wiki/Peace_be_upon_him