Extract Splitted RAR file into one, you Only need Extract PART1.
You can use Winrar For Android.apk or Winrar/7zip from PC.

How to extract Rar or Zip.
From Phone:
- Download one of this app from platstore.: Winrar for Android, Androzip, or Zarchiver.
- Launch app
- Search zip or Rar file you want to exract.
- Tap or press file to show option
- Choose extract file here.
- Done


How to extract Rar or Zip.
From PC:
- Download Winrar or 7Zip [Search from Google]
- Search zip or rar file.
- Click file and choose Extract file.
- Done