Upgrade Presta from 1.6.1.13 to 1.7.5.2

[Mujtabakiani]

Hello guys, Hope you are doing good.
I need some information regarding prestashop version upgrade.
Currently I am using prestashop version 1.6.1.13.
I want to apply this theme on my website https://addons.prestashop.com/demo/FO22367.html
But this theme is only supported in PrestaShop 1.7.1 - 1.7.6.0
So I want to upgrade my prestashop version to 1.7.5.2 with all existing data.
First of all give me advice that which version I need to upgrade to and secondly let me know how can I upgrade the vesion so that I can use that theme.
Your help would be much appreciated.
Thank you.