Data augmentation for WikiHow103

[cahuja1992]

As mentioned in Appendix A.2 that WikiHow103 is augmented using Backtransation using MarianMT (Junczys-Dowmunt et al., 2018). As quoted below

To generate ALIGNED samples, we create a para- phrase of each sentence in WikiText-103 through back translation using a neural machine translation model (Junczys-Dowmunt et al., 2018)

Can you please highlight the languages used for back translation with corresponding models ?
For example Helsinki-NLP/opus-mt-en-fr followed by 'Helsinki-NLP/opus-mt-fr-en'