I think you can search the keywords on Google, like audio merger, video joiner and so on. There you will get many only combing tools, like Clideo, Onlineconverter, FreeVideoJoiner, Kapwing, Fileconverto. But these online tools often insert the company logo to your videos automatically. Besides, if you want to merge fastly, you can try some offline tools, like Bandicut, Joyoshare Video Joiner, etc. Bandicut looks more complicated while Joyoshare has an intuitive interface fitting for beginners.