To be able to see any weapon skin you will need to install Optifine. Below we will explain how to install optifine.

Step 1: Download OptiFine from the official website: https://optifine.net/downloads
Step 2: Choose the version that matches your Minecraft version, then click Download.
Step 3: After download completes, locate the .jar file in your downloads folder.
️ Step 4: Double-click the .jar file to run the installer.
️ Step 5: In the installer window, click Install. Wait until it says "Successfully installed".
Step 6: Open the Minecraft Launcher.
Step 7: In the version selector, choose the new OptiFine profile.
️ Step 8: Click Play and enjoy your enhanced graphics!
Tip: For shaders, place shader packs in .minecraft/shaderpacks folder and select them in Video Settings > Shaders.