It would not be a Resident Evil game without a labyrinthine sewer level. Jill finds herself trapped in the sewer housing a secret lab in Resident Evil 3 Remake. The lab itself is locked down with an electronic door, and you will need the battery pack in Resident Evil 3 Remake to power these doors and escape. To start on your way, drop down the steep incline to the lower levels.
The path to the battery pack is guarded by multiple ferocious Hunter Gamma enemies. You will need the Shotgun to take these out. Wait until they charge at your with their mouths open, then blast them right in the face to take them down. There are several Hunter Gammas along the path at different points. They’re very resilient so be prepared to burn some ammo.
You will be able to save here, be sure to grab the MGL Grenade Launcher and the Explosive B compound on your way out. The Grenade Launcher can be used against Hunter Gammas if you’re out of Shotgun rounds. The best approach is to fire Flame Rounds into their mouths directly, this should one-shot Hunter Gammas.
The next path should be to the left, towards the lab, within this hallway there is a waterfall, behind which is a hidden alcove with some ammo in it, grab that. Go back the way you came and take the other tunnel to get to the Lab to your right. This second tunnel has the battery pack at the end of it inside the lab room. There are also some Flame Rounds on the ground to the right of the ladder that leads into this room.
Place the item in your inventory and remember to keep it with you as you will need it after the sewers as well.
Head back up the way you came, and back towards that first incline you dropped down into the sewers from. There should be a small ladder here to use to climb back up. Head over to the door and use the battery pack to progress forward. After using the Battery Pack and dispatching of the Hunter Gamma that hops out, head back through the yellow barred door and grab the Battery Pack. Head back through the barred door to continue on your adventures.