Restore to another messaging app

[Android Central Question]

I want to restore my backup to TEXTRA which is a downloaded messaging app. I already make it my default messaging app for my S6. But whenever I restore backup it always restore it to the "MESSAGES" app which is the default messaging app for S6. I cant seems to find away to transfer it to TEXTRA. I want to transfer it to textra because it has a date search for messages which is very essential also the reason why I want to backup my messages. My inbox is 20k in total btw, thats why I need the date function of TEXTRA.