Uh, I don’t believe in UFOs in the way that they are usually portrayed. But I agree that we are likely not alone in the universe.
Are you familiar with the Drake Equation? If not, you should be.
The Drake Equation represents an estimation of the number of civilizations in the universe with whom communication may be possible. It is estimated by multiplying (the average rate of star formation in our galaxy) by (the fraction of those stars that have planets) by (the average number of planets that can potentially support life per star that has planets) by (the fraction of the above that actually go on to develop life at some point) by (the fraction of the above that actually go on to develop intelligent life) by (the fraction of civilizations that develop a technology that releases detectable signs of their existence into space) by (the length of time such civilizations release detectable signals into space).
The last time I calculated this, based on intelligent estimations of each of those numbers, I’m pretty sure I got something between 5 and 10 other civilizations in our universe.