As such, there is no direct way to migrate photos from your OneDrive account to your Google Photos account. But you can definitely try other options like the desktop photo uploader and downloader tools that will help you migrate from OneDrive to Google photos. One such desktop photos uploader tool is PicBackMan. It automates the whole process so that you do not have to do much in terms of migrating photos from one service to another. Here's how PicBackMan Migrate process works.
Automate backup & migration of your photos & videos with support for all top services.
Trusted by users in 125+ countries.
“Your pictures are scattered. PicBackMan helps you bring order to your digital memories.”