a memorial service to remember those who have passed away
「法事」は英語で次のように言えます。
ーa (Buddhist) memorial service
ーa memorial service to remember those who have passed away
to pass away で「亡くなる」
例：
I went to Okayama Prefecture for my grandfather's memorial service the other day.
「先日、祖父の法事のため岡山県に行ってきた」
ご参考まで！
カナダ 
