Patch birth control question ??

Hello ladies , I dunno who uses the patch but I have a question?? I couldn’t find my birth control patches for a couple days , I was without them for about 3 days , but when I got them I put one of right away which would change my patch change day right ? And I used back up for 7 days after putting on new patch . So my question is , did I have to use backup for the rest of the month or just 7 days ? and did I mess up using the patch ? This is my first time using the patch, so I’m kinda worried I messed it all up this month. Please help.