Please look at the documentation for `emmeans::contrast`; it provides for such comparisons:

    library("emmeans")
    emm <- emmeans(m1, "Condicion")
    contrast(emm, list(
        `DB-DF` = c(-1,1,0,0,0,0),
        `NDB-NDF` = c(0,0,-1,0,0,0),
        `BB-BF` = c(0,0,0,0,-1,1),
        `DB-BB` = c(-1,0,0,0,1,0)
    ))

Note: This is based on the assumption that the levels of `Condicion` are in the order given in the question. If they are not, then they are probably in alphabetical order (the default) and you need to either permute the 1s and -1s accordingly, or create

    Datos$Condicion <- factor(as.character(Datos$Condicion),
        levels = c("DB", "DF", "NDB", "NDF", "BB", "BF"))

**and then re-fit the model** before using the above code to obtain the comparisons.