Plugin for footer

a plugin is generally not needed (and therefore might not exist) to change the footer credits of a theme;

look into footer.php or possibly functions.php of your theme;

for theme specific suggestions, please post in your theme’s deirect support section.

I cant find proudly powered in footer
Theme is: https://www.ads-software.com/themes/houston

as already suggested, please post in the theme’s forum at https://www.ads-software.com/support/theme/houston