You would want to want to pick the one for the industry that you are most involved in, if you can’t pick one that represents your whole business. Here are just some suggestions:
323113 Commercial screen printing Ex: art works, screen printing without publishing
541430 Graphic design services ex: silk screen design service (serigraphy)
541490 Other specialized design services ex: textile design services
611110 Elementary and secondary schools ex: teachers
611210 Community colleges and C.E.G.E.P.s ex: teachers
611310 Universities ex: teachers
611510 Technical and trade schools ex: teachers
611610 Fine arts schools ex: teachers
611690 All other schools and instruction ex: teachers
If none of these fit your needs, you can search for others on this website: https://www.statcan.gc.ca/eng/subjects/standard/naics/2017/v3/index
If you have TurboTax Live Assist & Review, here is how to talk to a Tax Expert: https://turbotax.community.intuit.ca/community/navigating-turbotax/help/i-m-using-turbotax-live-assist-review-how-do-i-talk-to-a-tax-expert/00/873764