Well they are two different things. Moving photos, music, videos, etc. (not apps) can be done through file manager apps. Some systems come with some already, others you would need to download and install an app of that type. However, in most cases, you can't move all files at once.
Now you can connect the device, via USB cord, to a computer and open up the memory like you would any folder on the computer. Then move the files over to the card. All at once.
You may also then want to access the apps you use to make those items (camera, etc.) and go into their individual settings and set it to save new files to the card.
Now with apps, that is a whole other game. The following is necessary for that...
NOTE: The above and below are not compatible. Should you choose to do the following, do not attempt the above first as it will get the data wiped and you would lose it. Wait until the changes below are made and then you can do as needed for the above files.
First, you need to be using a phone that is running at least Android "Marshmallow" or be able to upgrade to it. Second, you will need the instructions I am including below. And third, you need a phone that has not been restricted by the manufacturer from making this change. Which does happen.
NOTE: If any of the steps are missing on your phone, or they don't work for you, then you have a phone that either has an older Android version or has been restricted by the manufacturer.
How to turn the "External" SD card into "Internal" storage on "Marshmallow".
NOTE: Please be sure you start with a blank SD card. It needs to be blank because when the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device).
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your phone.
NOTE: If you don't reboot the phone, many things may not work correctly, so make sure you do.
How to turn the "External" SD card into "Internal" storage on "Nougat".
IMPORTANT NOTE: Be sure you start with a blank SD card. When the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device), so anything on it prior would be gone.
1. Go to "Settings", and then select "Storage & USB".
2. At the bottom of the list you should see the SD card's details, including the option to format it and make it "Internal" storage.
3. Once this is done, reboot the device and you can start running things from the card.
If you don't reboot the phone, some things may not work correctly, so make sure you do the reboot.
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