Really stuck with FOLDER STRUCTURE for SEO

Looks like index.html in each folder is the way to go..

But now I am having a problem with redirects...

right now, I have example.com redirecting to xyz.example.com and it works fine etc....

But...if I add anything onto example.com such as example.com/cars/ or anything.... it will NOT REDIRECT to xyz.example.com/cars/...it leads to the search engine not finding anything...and shows my local internet companies search saying can not find xyz.example.comcars with no slash.

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Search Engine Optimization|Web Design Orlando