on my way to school ,I saw a wallet on the ground and I picked up it

把最后picked up it 改成picked it up

应该把句子最后的 up 和 it 互换一下。
On my way to school ,I saw a wallet on the ground and I picked it up.

pick it up == pick up the wallet

用 it 指代时，应该把代词放在中间。