There are fallacies galore here.
Number one: Appeal to authority. "The poor worry. The rich don't worry". Says who? This is totally contrary to everything I know about the behaviour of people.
Number two: Not understanding causality. The claim is that there is a 100% correlation between poverty and worries. That doesn't mean that one of them can be changed at will. Actually, it makes it unlikely that one of them can be changed at will. If that correlation were 100% (which it isn't, see number one), we would all suspect that when you are rich, there is nothing that could make you worry, and when you are poor, there is nothing that can stop you from worrying. We wouldn't believe that you could stop worrying at will and become rich that way. We would instead believe that a rich person wasting their money would become poor and start worrying, and that a poor person starting a successful business or winning the lottery would become rich and stop worrying. Not the other way round.
Number three (already pointed out), "affirming the consequent". If we had the two statements given, plus the statement "Everybody is either poor or rich, and everybody either worries or not", then the conclusion would actually be correct, but that isn't the case. But let me add a third statement that is probably more justified than the two original ones: "Dead people don't worry". Now the advice given can be literally fatal: Stop worrying, and you will either become rich or you will die.