Shopify Theme Custom Code Migration

I need custom CSS and HTML codes copied from my current Shopify theme to a new theme. The codes need to be transferred exactly as they are, with no modifications.

The specific parts of the site that require code copying are:
- Product pages
- Collection pages
- Cart pages
- Packing slips
- Invoices

Ideal skills and experience:
- Proficiency in Shopify
- Experience with CSS and HTML
- Attention to detail for exact code copying