We have found 4 software records in our database eligible for .odp to .pptx file format conversion.
OpenDocument format based presentations (.odp) which are typically saved using some open source presentation programs, such as OpenOffice Impress / LibreOffice Impress.
The easiest way to produce a PowerPoint presentation (.pptx) would of course be to use PowerPoint itself. However, if you do not have access to the program you also can use some of the alternatives that support PowerPoint formats, as all should be capable of odp to pptx conversion.
ODP
An odp file extension is used for OpenDocument presentation files. OpenDocument presentation files are created by Impress presentation application that is a part of office suites that are based on free OpenOffice.org suite (OpenOffice.org, LibreOffice, StarOffice etc.). Microsoft Powerpoint is also able to open OpenDocument presentation files.
PPTX
Files with pptx extension are presentations from modern version of PowerPoint from Microsoft Office / Office 365. PowerPoint slide shows are basically set of screens which can include text, graphic, sounds or videos used for various presentation purposes.