[お墓](https://eikaiwa.dmm.com/uknow/questions/32541/)はgrave,[命日](https://eikaiwa.dmm.com/uknow/questions/7947/)はmemorial day、[お盆](https://eikaiwa.dmm.com/uknow/questions/10913/)はthe Bon holidays, [お彼岸](https://eikaiwa.dmm.com/uknow/questions/49580/)はHigan weekでOKですので、質問者様の書かれた文を英訳すると
We have a custom where we pay a visit to our family's or friends' graves and pray on their memorial days or during the Bon holidays and Higan week.
Every year we visit my mother's grave and place incense in front of it.
We should visit the graves of our ancestors every holiday.
お墓参り visiting a grave
先週の日曜日に叔父のお墓参りした。
We visited my uncle's grave last Sunday.
毎年、私たちは母のお墓参り、その前に香を置きます。
Every year we visit my mother's grave and
place incense in front of it.
私たちは休日ごとに先祖のお墓参りです。
We should visit the graves of our ancestors every holiday.