How to download my invoice of Mac book

The invoice information for retail and online stores is at:

Viewing & Changing Orders - Shopping Help - Apple

View or Print Invoice

"Once an item is shipped or picked up, Apple will create an invoice for your order. To view or print your invoice, go to your Order Listing page and select an item to go to the order details. Then, select View Invoice at the top of your order details page to access your invoice.

If you need help viewing or printing your invoice, speak with an Apple Specialist" Telephone numbers --> Contact Apple for support and service - Apple Support

I would provide links and telephone numbers but they depend upon the country settings you are using. It is best if you just go to the document yourself.

Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support