I would try and clean up the S3 first, but most Android malware is from an app you downloaded. Use this Anti-malware app to see if S3 is infected. https://forums.androidcentral.com/e...d=org.malwarebytes.antimalware&token=m7610Ey5
And when you transfer data, depending on how you do this (phone to phone) should be safe. I would RE-install my apps from playstore a few at a time, which should be safer than transferring any from older phone.