How to exclude just one page from https?

Try to figure out this code. This might work. Best of luck!
<IfModule mod_rewrite.c>
RewriteEngine On
# Go to https if not on careers
RewriteCond %{SERVER_PORT} =80
RewriteCond %{THE_REQUEST} !/careers/[\s?] [NC]
RewriteRule ^(.*)$ https://www.mywebsite.com/$1 [R,L]

# Go to http if you are on careers
RewriteCond %{SERVER_PORT} !=80
RewriteCond %{THE_REQUEST} /careers/[\s?] [NC]
RewriteRule ^(.*)$ https://www.mywebsite.com/$1 [R,L]
</IfModule>

Where I put this code? Thanks

Try putting it in your .htaccess file & see if it works.