I have to deal with all the laundry that's accumulated.
I have to wash all the laundry that has piled up.
I need to deal with all the laundry that has piled up.
「溜まった洗濯物をまとめて片付けなきゃ」= I have to deal with all the laundry that's accumulated. / I have to wash all the laundry that has piled up. / I need to deal with all the laundry that has piled up.
ボキャブラリー
have to/need to = ~しなきゃ、~する必要がある
deal with = 処理する、片付ける
laundry = 洗濯物
accumulated, piled up = 溜まった