Disabling default Canonical line

Hi everyone,

By default, wordpress automatically added the following line to all of my child subpages – <link rel=’canonical’ href=’https://www.site.com/subpage&#8217; />

Therefore, 250 of my pages got wiped out of the google index. Does anyone know how I can disable it? I searched google and it told me to add a line to functions.php but I don’t have that file with my theme.

I tried this plugin but it didn’t work: https://www.ads-software.com/extend/plugins/disable-canonical-url-redirects/

Any other suggestions?

Thanks