
The combination of "si" + imperfect subjunctive + conditional in Spanish is used to express hypothetical situations or actions that are dependent on a certain condition being met. The "si" introduces the condition, the imperfect subjunctive expresses the hypothetical action, and the conditional indicates the result or consequence of that hypothetical action.
We are given four forms of the verb "viajar" (to travel) in the imperfect subjunctive (imperfecto de subjuntivo).
Let's see what is the conjugation of that verb in the imperfect subjunctive:
VIAJAR (imperfecto de subjuntivo):
Yo viajara
Tú viajaras
Él / ella / usted viajara
Nosotros / nosotras viajáramos
Vosotros / vosotras viajarais
Ellos / ellas / ustedes viajaran



The subject of the sentence is "ella," so we use the third-person singular.
Our sentence becomes:
Si [ella (viajara) a Buenos Aires], le gustaría ir al Museo Evita.
Translation: If [she (traveled) to Buenos Aires], she would like to go to the "Museo Evita."

The [condition introduced by "si"] is put in brackets.
The hypothetical action is bolded.
The result of the hypotecal action is underlined.