Diversification and international stocks

I’m satisfied with the performance I have received over the last 25 years from Vanguard and Fidelity mutual funds. I’m married, retired and in my eighties.

What does the gang here feel is a good method or tool to use to choose the ETFs to replace my current holdings in mutual funds, like VWENX, to ETFs?

Also, any suggestions for choices in long-term ultra-conservative investments currently available in Vanguard & Fidelity?