If you’re replacing the SIM card you just need a sim ejector tool or an unfolded paper clip will do just fine. The SIM tray is located at the top of the S8. https://www.verizon.com/support/knowledg...-base-211254/#:~:text=From%20the%20top%20edge%....
If you used a particularly cheap cable from Amazon, eBay, Wish, AliExpress, or any other retailer that sells cheap cables, you might have damaged TriStar. What happens when you flip the cable’s orientation around? Does the same issue happen? For context, TriStar is a USB validating chip. Apple designed that chip to detect whether or not the accessories you’re connecting are certified, even from aftermarket manufacturers. The reason being is apple designed a special circuit board that is attached to the lightning connector that talks to TriStar. On this proprietary circuit board there’s built in surge protection. Apple sells this circuit board to third party manufacturers and cheap accessory manufacturers don’t have proper surge protection which results in damage to TriStar and can lead to the issue you’re experiencing. There’s a tool you can buy to test it yourself but they’re around $150 or call around your local repair shops and see if they have a TriStar tester.
was the battery connected when you connected the display? sometimes people can blow the backlight circuit when they connect the screen while the battery is connected. If you shine a flashlight on the display while attempting to wake it up or turn it on that's a quick and easy way to diagnose a blown backlight. also what did iTunes say when you connected the device? Was it in recovery or DFU mode?
If this is your first attempt at a repair it might be worthwhile to let someone experienced fix it. I’m not trying to discourage you from attempting to fix what you own, it’s just a very expensive part to replace. But my advise is to pick up a heat gun or a heat mat like this one (https://www.mobilesentrix.com/cpb-heat-mat-station) and take your time, especially around the FaceID assembly. If you damage that it’s very expensive or impossible to fix. If you use the heat mat, lay the iPad with the backside resting on the heat mat for a few minutes at a time at around 80C. This will heat up the frame and therefore heat up the adhesive holding the screen. If you lay the iPad on the heat mat with the screen facing down you run the risk of damaging the display. If you’re using the heat gun, heat the screen itself up to where it’s almost barely too hot to touch.
You’ll want to order the Pro Tech toolkit as it will have everything you’ll need and more to fix your iPad and other devices if need be. Pro Tech Toolkit You can find replacement screens for the 8th gen on either Mobile Sentrix, Injured Gadgets, or Mobile Defenders. Mind you it’s just the parts you’re buying from them and they’re the top 3 parts suppliers and they back their parts with a solid warranty. Just create an account and order what you need!