It really is important you set up some kind of backup solution, and do it now. Do not wait there's actually a serious problem with your phone (it fails or gets damaged, or it' lost or stolen), and there's the possibility of losing those photos and videos of your loved ones.
Samsung provides a 'Smart Switch' utility, which is a multi-function maintenance program aimed primarily for Samsung devices. One of them is the backup and restore function, which will allow you to do a full backup of your data (including those photos and videos) to your PC.
https://forums.androidcentral.com/e...%2Fowners%2Fapp%2Fsmart-switch&token=TB4v8cGO
You might have to rely on your A3's WiFi only for this, I don't know if it supports this over a USB cable, specifically OTG support (depending on which model A3 you have -- the original 2014 model might not support OTG, the later 2017 model is more likely to).
https://forums.androidcentral.com/e...%2Fowners%2Fapp%2Fsmart-switch&token=TB4v8cGO
Another option is to install the Google Photos app. This won't allow you a full, comprehensive backup of your data but it will apply to your photos and videos. The app includes a backup and sync function that will upload your entire photo and video library into your online Google account, and it runs automatically in the background. You'll have a duplicate of your photos and videos stored on your A3 and in your online storage, so you can view them either on your phone or your computer by going to:
https://photos.google.com
After installing the app, be sure to go into the app's Settings menu to set the app up accordingly. Also, you might not even want to use Google Photos as a photo manager app. Some people prefer the user interface of the Gallery app that was already on their phones. In that case just continue using the Gallery app as your photo manager and just leave Google Photos as the background backup service.
https://play.google.com/store/apps/details?id=com.google.android.apps.photos&hl=en_US&gl=US