How can I transfer a Minecraft Java Edition save to Minecraft Windows 10 (Bedrock) Edition save? [duplicate]

For the textures, you can easily change it by changing the terrain.png file with your desired texture pack. But beware that PC's terrain.png may vary with PE's. Try searching for a similar or exact texture on the Minecraft Forums. They have lots of ported texture pack.

For maps, you will need to first port it because MCPE maps aren't infinite and a portion of the world will need to be cut, pasted and then saved in MCPE format. Then you can transfer it to your Android device.

Note: My previous answer was for iOS devices. I have changed my answer to fit the question and hope it helps.