Latin is a flexive language, which means the "function" of the words is in the case desinences. The cases are Nominativus, Genitivus, Dativus, Accusativus, Vocativus, Ablativus (Locativus is often left out). These desinences also vary according to the declination, latin has 5.
The name (substantivus) pater belongs to the 3rd declination.
Pater is the nominativus (singularis), Patr-is is the Genitivus, Patr-i the Dativus, Patr-em the Accusativus, etc.
"To my" (father) can be expressed with the Dativus, whose desinence in this case is -i, so the word you need is "Patri".
This is a very short and incomplete explanation of why you need Patri instead of Patris or Pater.
I don't know if you meant something like "in memory/honour of my father", in that case it would be "In memoriam/honorem patris mei".
I hope this helps.
ya that helps a lot cuz i kinda understand it now...but we kinda wanna say it like it's a gift/tribute to our dad...so how would u directly translate "to my father"...like im getting this tattoo as a gift "to my father" .... or maybe like "to my dad" or "to my daddy"