Can lock my phone if my phone someone stolen already turned off find my iPhone

Odds are that someone with it merely erased it with iTunes, which breaks the Find My remote tracking and controls. In that case, no, you cannot remote lock it now (did it not already have a screen lock passcode in use?).

But, if you login to www.icloud.com and it is still listed under your devices, activation lock remains in effect.

If Find My Phone has been turned off, you can't lock the phone.

Do you mean someone turned off the phone, or someone hacked your Apple ID and turned off Find my iPhone?