Hammad I would encourage you to read Alex Hormozi’s $100M Leads book, it will give you the base knowledge that you would need to understand about getting leads & reach outs . You can also find the free course on his website acquisition.com - however, cold email can be effective, as well as cold dm’s. Also try to build your list while doing this.
Eddie I personally use a lead broker for this to get in-market leads meaning if I tell them my potential clients are searching this type of keywords they will pull a list for me of people that are actively searching for that, that is what makes it "in-market". I do not know of a software that does this. Also to mention this only work for the US