・・・。
I don't know what to say...
Literal
What [quotative-と] said-[if-たら] good [embedded-question-か]...
何と言ったらいいか literally chains 'what should I say [if I say it]?' — an embedded question expressing speechlessness — and is trimmed off here without the usual わからない ('I don't know'). The trailing ・・・ does the work of conveying uncertainty or speechlessness. This kind of unfinished sentence (言いさし) is extremely common in Japanese, where leaving things unsaid is often more polite or evocative than completing them.