There doesn't seem to be much detail available online about the Exeter blitz. Historic England publishes an aerial photograph of the damage in Exeter (though confusingly it seems to be presented with North at the bottom) at https://historicengland.org.uk/services-skills/education/educational-images/bomb-damage-exeter-10242 .

However, the official records are available at The National Archives - see the TNA research guide at https://www.nationalarchives.gov.uk/help-with-your-research/research-guides/bomb-census-survey-records-1940-1945/ - though unfortunately these records haven't been digitised for download. A freely downloadable dataset listing the 32,000 bombing raids on Britain in WW2 compiled from intelligence reports in The National Archives is available at http://www.warstateandsociety.com/Bombing-Britain. According to this dataset, raids on Exeter St. Thomas which caused the most casualties occurred on the nights of 23/24 April and 24/25 April 1942 and TNA's Discovery catalogue lists reference HO 192/868 as providing details of the damage caused.

If you can obtain a copy, I understand that the HMSO publication "The Defence of the United Kingdom", by Basil Collier, HMSO, London 1957, is meant to provide a good account of the so-called 'Baedeker raids' on Britain. A contents list is available at https://www.ibiblio.org/hyperwar/UN/UK/UK-Defence-UK/index.html from which it would appear that the Baedeker raids are described in Appendix XXXVI (The Führer's Order for the 'Baedeker' Offensive) and a bomb map for the Exeter raid of 3 May 1942 appears as Map 28 (The Bombing of Exeter, Night of 3rd May, 1942).