To keep all those fish, honestly, your going to need something HUGE. I've seen countless accounts of Jag's taking over full 6 ft. tanks (when full grown and if their males). If your convicts breed thats going to cause problems, and if your JD's breed that will cause more problems. I know Tilapia get huge, and I don't know much about their agression levels but I'd be willing to bet they aren't going to work in anything under a 6ft tank with those others, and again if the Chocolates start breeding you are going to have problems.
I'd say in order to keep all those fish together for life you'll need a tanks with that is 6ft long. IF you want to have them in seperate tanks, you could probably leave the cons in your 70 litre(I'd like to know the dimensions of that though) and IF you have a male and female JD you could probably do them in a 55 in and a few of something small, like liverbearers, or a smaller variety of pleco (you could have few depending on the speccies). The chocolates are listed with a minimum tanks size of 75 gallons(284.25 Liters)for 2. The same goes for the Tilapia. You've got several fish that need a lot of space, and all of which are pretty messy (they are cichlids afterall). I would suggest taking the advice previously given and take these fish back. Keep the cons for now, if you do end up getting a biggers tank look through the species profiles here and on other sites, ask questions (preferably before you buy), and then decide what kind of stock listing is best suited for your tank.
Please understand, I don't mean to come off as rude, but it makes all of us angry here when LFS's misinform pet owners just to make a sale, or simply because they don't care what they are selling to whom. It situations like this, one that is obviously not your fault since you trusted someone you thought to be a knowledgable professions, that really strike a nerve with me.
