Adding tax and recalculating all?

[luffee]

Hello,

I have been using virtuemart in my store for a long time, since joomla 1, at that time store was simple and we didn't need much, so all our prices were listed without any calculation for tax.
Over the years we upgraded and migrated multiple times, and the store evolved and expanded, now I need to add tax calculation rule, but I have over 6000 products.

How can I add tax calculation rule and have it recalculate all base prices from final price with tax included?

I am using Joomla 3.4.8 and virtuemart 3.0.12

Thank you in advance