My 3ds isnt cfw but have blackscreen any suggestion please?

I buy my 3ds second hand but good condition with no issue and this is my forst time having a 3ds console and the 3ds have already 2gb sd card and then i change my 2gb sd card to 8gb micro sd card with adapter because i have plan soon to cfw my 3ds to have lot of games and space so my micro sd card with adapter i format in my 3ds i thought that formatting in 3ds is only the sd card format hays but all the system was format and i notice my 3ds is slowing the system and after a few hours my 3ds wont turn ON but it charged but my 3ds still charged and i do everything like remove the battery then put it back then turn ON and remove the sd card then turn ON and also the press L+R+(D-Pad)A then long press or press then ON and all of that if wont work please help me this problem hays