Permalink Issue

I have a blog and this permalinks and stuffs are pretty new to me.I
have a specific problem.In my blog i changed my permalink which
displays my post name,and month and year.But thing is i need to put a
index.html before all these.If i don’t do that my detailed posts goes
to a 404 page.I have tried goggling and tried lot of tricks and tips
from different websites,but nothing is happening.Please take look at
my blog then you will come to know.
https://www.techdunes.com , i really want to remove this index.html from my
URl .Please reply me in details,I would be greatful to you.

Thanks and Regards
Techdunes