Export image with guides

[rich2005]

You can not keep the guides when converting to any of the 'export' formats png, jpeg, tiff... These are flattened 'final-for-use' images.

psd and gimp .xcf are 'working' formats that can retain more than just the image.
Save your work in Gimp xcf format. This saves layers, guides, grid settings, active selections and channels.
When complete then export to a jpeg.