The Wemos is 3.3v, as is the digital signal it sends to the LED strips, but the strips can easily read that signal.
However, they require their own separate 5v supply (just share the ground between all power sources) and enough current (Amps) to handle the total number of LEDs… which can vary depending on colour, intensity and number of LEDs… check with the suppliers for those requirements and then add in a little extra as a buffer… you can never have too many amps available 
EDIT - I guess I should expand a bit on my explanation… the ESP chipset runs on 3.3v as does the GPIO, but many ESP development boards will be powered by 5v from the USB connector… they actually have their own 3.3v regulator on them in order to accommodate that.
So generally in this use case the ESP dev board gets powered by the same 5v power supply that runs the LED strips.
Google NeoPixel and you will see many explanations on how they are wired up to Arduinos and ESPs.
for example, I have made my own power distribution boards for the Wemos D1 Mini to take a 5v PSU and run both the Wemos and RGB strips from it.