Translation:We will have found him in two hours.
Lo habremos encontrado a él en dos horas.
Lo is a direct object pronoun which can mean any of "it/him/her/you (formal)", without further context it's impossible to know which. So in Spanish (where the context is not clear) it's common practise to add " a él" or "a ella" ect. to clarify the subject.
So this effectively breaks down to
"Lo habremos encontrado" = "we will have found it/ him/her/ you (formal)"
"a él" = clarification of "lo" to show we are talking about him (ie Pete rather than John, or even Pete rather than the car)
"en dos horas" = in two hours
And just to really mess things up I think you can put those three sections into any order. ie.
en dos horas a él Lo habremos encontrado etc.
It is the required direct object pronoun for him. Lo habremos encontrado = We will have found him. Since lo is also the direct object pronoun for it (masc.) and for you (formal masc.), the optional a + pronoun phrase (a él) is added for clarity. The lo is required; the a + pronoun phrase is optional.