Use the Mimeo Photos Import Service to purchase projects that you created with older versions of Apple iPhoto/Photos.
In your project, hold the option key and click on the Buy Book option in the top right hand corner.
OR If you have already upgraded to macOS Mojave 10.14 (Photos 4).In the top right hand corner of the Apple Photos window, click Export PDF and Export to PDF in Mojave.
To upload a PDF, follow these simple steps:
1. Navigate to https://import.mimeophotos.com
2. Drag and drop your Print Ready PDF or click Upload Print-Ready PDF
3. Follow the remaining prompts to purchase your project
4. After the upload process is completed, simply provide shipping and payment details and click Submit
5. You will receive an email order confirmation once complete
For more articles on using the import site:
Creating an Apple iPhoto or Photos project Print Ready PDF