Oh, dear 
184 layers 3000 x 3000 pix 7.4 GB in memory.
To make it more manageable, crop it down to a tiny size. say 10 x 10 pix
Use the align tool to spread those out into a strip.
Fix the image using Image -> Fit canvas to layers
Now you can use the palettes context menu to make a new palette.
A quick demo: https://i.imgur.com/ZsIN3IV.mp4 only using 19 layers but the same for your 184
184 layers 3000 x 3000 pix 7.4 GB in memory.To make it more manageable, crop it down to a tiny size. say 10 x 10 pix
Use the align tool to spread those out into a strip.
Fix the image using Image -> Fit canvas to layers
Now you can use the palettes context menu to make a new palette.
A quick demo: https://i.imgur.com/ZsIN3IV.mp4 only using 19 layers but the same for your 184