Opening .obj Files and Exporting Textures
Step 1: Open Blender

Open Blender on your computer. If you don't have it installed, you can download it for free from Blender's official website.
Step 2: Import .obj File

In Blender, click on File in the top-left corner.
Select Import and then choose Wavefront (.obj).
Navigate to where your .obj file is saved and open it.

Step 3: Check Imported Object

Once imported, you'll see your object in the 3D view. Use your mouse to rotate, zoom, and pan to explore it.
Step 4: Export Textures

Switch to the Layout workspace by selecting it at the top.
Locate the Material Properties tab on the right side (a round sphere icon).
Find the material list and for each material:
Click on the material name.
Scroll down to the Settings panel.
Click Browse next to the Texture field and save each texture image.

Export Textures Separately

Save each texture image separately by right-clicking on the image and choosing “Save As”. Choose a location on your computer and give it a name.
Exporting as .DAE (Collada) File
Step 1: Switch to Modeling Workspace

Click on Modeling at the top to switch to the Modeling workspace.
Step 2: Export as .DAE

Click on File in the top-left corner.
Select Export and then choose Collada (.dae).
Choose a location to save your .dae file.
Set any additional options if needed.
Click Export COLLADA.

Step 3: Finished!

You now have a .dae file that can be used in various 3D applications.