If you are able to export CSV files from Lightspeed, then you can use this automated tool to migrate your data in CSV to Shopify store. The tool works smoothly (I tried its free demo and read many recommendations about them on other forums) and with very reasonable price. Contact its support team via live chat for further information.
Hope this helps!
How did you conversion go? Are you happy with Shopify POS? I am actually thinking about moving from Shopify POS to Lightspeed, as Shopify is planning on charging $89/month for their POS product starting in October. Considering how lacking the Shopify POS system is for inventory, reporting, and general POS required workflows, I am surprised Shopify decided to charge more for this than their actual eCommerce product (which is $79). Why did you decide to move away from Lightspeed? I hope you are having a good experience with whatever platform you moved to. Thanks.