Hi,
I am interested in your project.
I have experience on website development. Special is on Opencart.
https://www.freelancer.com/u/Ginjag.html
I upgrade and ensure to keep all your data such as orders, customers, products and catgories.
You need to give me all modules can work with Opencart 3.x
Please feel free to contact me and we start.
Hope to work with you.