Google today announced availability of “Dark theme” on its Play store app for all Android smartphones. The availability so far has been limited because of phased roll-out.
— Google Play (@GooglePlay) March 11, 2020
You can check for the Dark theme setting option by navigating to settings and then to theme. If you are on Android 10 you can choose “system default” as the option apart from Light and Dark. This option allows system-wide Dark or Light theme option to apply to Play Store as well.
If you are on other Android versions where “default theme” option is not available you can choose from Light or Dark theme options.