Digital images do not need a ppi. The exported image at 1000pixels long edge will always be 1000pixels, it will look exactly the same if an embedded ppi is 300, 240, 1000, or even 1. A ppi value only becomes relevant when determining an image size for printing.
Lightroom does not have the facility to define the ppi other than what you get! IMO Your (default) 240ppi export will be quite OK.
You could change to 300ppi with other software (Photoshop) if the "company" insists, but it will not change the 'quality' of the image whatsoever.