We have found 2 software records in our database eligible for .docx to .pages file format conversion.
Pages (formerly iWorks Pages) can import and open Microsoft Word documents (.doc, .docx) just fine, so there is nothing more easier than resaing .doc files as .pages file. This of course is only possible if you have access to macOS/OS X/iOS platform.
Without the actual program it will be very hard to reliably produce .pages documents. Some on-line converters claim that they support doc to pages conversion (for example ZAMZAR), but they often save to some previously used format and may not support latest versions.
DOCX
Files with docx extension are documents written and saved using Microsoft Word word processor edition 2007 or later. DOCX format replaced the previously used DOC format, moving from binary files to Open XML schema-based documents. They are supported in almost every modern word-processing tools.
PAGES
pages file extension is used for default document format of Pages, a word processor and page layout program from Apple. No other program can open the .pages files, but Pages is able to export its documents to some other formats, such as PDF or Microsoft Word's .docx.