I'm assuming you're talking about Terrene on Android and not on PC?
If so, saves for Ren'py games on Android will be deleted and lost forever, if you uninstall the previous version of a game, without transferring saves beforehand.
What you need to in the future, so you can use your save files from previous versions on newer versions of Terrene,
Is find your "My Files folder/internal storage" on your Android device. Look inside your storage for an "android folder/data folder", and find a folder called com.android.terrene_0_0_4 inside that. (This is the folder for version 0.04 of Terrene).
Then, copy the files/saves inside com.android.terrene_0_0_4 to a new folder, outside of the com.android.terrene_0_0_4 folder of your choosing. (Basically, make a back up version of your saves).
Start up/install the new version of Terrene, so it initializes and then copy the saves you stored before, into the new version's folder. (For example copy the saves into com.android.terrene_0_0_5 / v0.05 of Terrene.)
After, you can delete the old/previous version of Terrene.
However, this will only work if the next version of Terrene is compatible with older save from other versions, otherwise the game won't run correctly with older saves.
I mention in the changelogs for the Terrene updates, what the new version is compatible with, so check the change logs on my patreon/itch for the version you want to run/if the saves are compatible.