If you want to use, you should use textures/items/arrow in your plugin config/script. NOTE: Textures should work even if the Minecraft server does not register or support some vanilla Minecraft items or blocks, because textures are rendered client-side, as long the textures remain unmodified by custom textures. the directory separator should be a forward slash (/),.

If you want to use the vanilla Minecraft Bedrock textures for plugins (PocketMine-MP), If you don't have Git installed, you may try downloading and installing Git here.