As the translation states, "if I CAN meet with my friend", not just "if I meet with my friend". 会う "meet" here is changed to 会える "can meet", so the -ba form becomes 会えれば "if can meet".
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As the translation states,
As the translation states, "if I CAN meet with my friend", not just "if I meet with my friend". 会う "meet" here is changed to 会える "can meet", so the -ba form becomes 会えれば "if can meet".