need to fix the non exist page redirection issue

my hosting is on hostinger i had my abc.com working well and i had put some backlinks aswell ... which were redirecting to some of my pages like abc.com/what-ever but now i had to redirect my root domain ABC.com to abc.com/mp . so because of previous backlinks whenever someone clicks those links as they were already abc.com/what-ever and that page does not exist as now main domain is abc.com/mp ..it doesnt redirect to abc.com/mp and shows the following error...

Oops, looks like the page is lost.
This is not a fault, just an accident that was not intentional.

all i want even person write wrong url related to my site or click on the page which doesnot exist ..it will redirect to https://abc.com/mp and if the page exist it goes to that page