How do I know which version of Minecraft I have?

Solution 1:

Simply look at the bottom of Minecraft's title screen.

At the bottom right or bottom left, you should see a number. (1.14.4, 1.13, etc.)

If the number is in the bottom left, you are using Java Edition, also evident in the subtitle below the main title.

If the number is in the bottom right, you are using Bedrock Edition. This is evident because Bedrock Edition just uses the title Minecraft with no subtitle. The number itself is the version number.

Solution 2:

It should be pretty simple:

In Java edition your Minecraft version will be shown in the lower left hand corner of your screen.

This is Java edition, but is essentially the same for Bedrock edition except it should be on the other side corner like this.