Word document missing pages when opened on MacBook after conversion from Pages

Since Pages is not a Word clone, it only knows how to translate certain features of Word documents into Pages internal document format, or on export, the reverse of this translation process. The original Word document is not available for editing and does not remain open after the Pages translation completion. What does remain open is a new Pages document. This is the behavior on all Apple devices supporting Pages, and Apple does not guarantee the translation process.

When you know you will be exchanging Word documents with another person using Word, then you should be using the same version of Microsoft Word to converse in native document format. What you see in Word, your tutor will see when they open your Word document and vice-versa.

You cannot trust Apple's Quick Look to display exactly what a Word document will look like when opened in Microsoft Word. Two different worlds.

If the only two applications installed are Pages and TextEdit, selecting the Open Attachment menu item by right-clicking the Word document will default to opening in Pages if it is installed or TextEdit otherwise. If you have other applications installed that can open Word documents, then you want to use the Open With menu items. And if you have Word installed as I do, the default Open Attachment will open the Word document in Word, not Pages or TextEdit.

I don't have Word installed on my iPhone or iPad, and never use OneDrive, so won't be able to test those issues here. Pages on the i/Pad/OS platform is implemented differently than on the Mac, just as i/Pad/OS itself is different from macOS (different developer's kits) and hardware.

Pages will open to the last saved file location (e.g. OneDrive) so that may explain things on your iPhone. If you are using Word on the iPhone, that will likely be the default application used by Apple Mail on that platform, and opening in OneDrive too. Without Word installed on the Mac, it will default to Pages there.