here are two solutions for you for your tb-8504f… the first option is for if you only damaged the top layer of the screen. youll want to tear down the unit ( videos linked) and then test the layer under neath for functionality. if it is damaged, solution 2 will replace both the top and bottom layer of the screen. again, video is linked. good luck.
replacement of digitizer screen only:
https://www.youtube.com/watch?v=eG56FmSPHwU
https://www.deviceparts.com/screen-replacement-for-lenovo-tab-4-8.0-tb-8504f-black-ori.html
replacement of digitizer and lcd panel:
https://www.youtube.com/watch?v=3k1G0ctzEl0
https://www.amazon.com/Display-Assembly-TB-8504F-TB-8504N-TB-8504X/dp/B07CWJTJTC