The size of the event horizon of a black hole depends on the mass of the black hole. The greater the mass, the larger the radius of the event horizon.

One idea you may have heard is that black holes go about sucking things up with their gravity. Actually, it is only very close to a black hole that the strange effects we have been discussing come into play. The gravitational attraction far away from a black hole is the same as that of the star that collapsed to form it.

So, if you are a star or distant planet orbiting around a star that becomes a black hole, your orbit may not be significantly affected by the collapse of the star (although it may be affected by any mass loss that precedes the collapse). If, on the other hand, you venture close to the event horizon, it would be very hard for you to resist the “pull” of the warped spacetime near the black hole. You have to get really close to the black hole to experience any significant effect.

If another star or a spaceship were to pass one or two solar radii from a black hole, Newton’s laws would be adequate to describe what would happen to it. Only very near the event horizon of a black hole is the gravitation so strong that Newton’s laws break down.

https://wisconsin.pressbooks.pub/astronomy/chapter/chapter-24-section-24-5-black-holes/

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solar radius is a unit of distance, commonly understood as 695,700 km and expressed as R⊙{\display style R_{\odot }}, used mostly to express the size of an astronomical objects relative to that of the Sun, or their distance from it.

695,700 kilometres (432,300 miles) is approximately 10 times the average radius of Jupiter; 109 times the 6378 km radius of the Earth at its equator; and 1/215 {\textstyle {1 \over 215}} or 0.0047 of an astronomical unit, the approximate average distance between Earth and the Sun.

https://en.wikipedia.org/wiki/Solar_radius

At about 0.01 au (two solar radii would be 0.0094), the sun as a black hole would not affect the Earth, nor Venus, nor Mercury.

Mercury is 0.4 astronomical units away from the Sun

https://science.nasa.gov/mercury/facts/

Based on that, we would stay put. A black hole does not emit light, including sunlight. Sunlight warms our planet (so it’s going to get mercilessly cold). Many plants would die and they would stop making oxygen. And while you can argue that we can’t live without heat from the sun, with 8 billion humans plus all the animals on the planet, I suspect we’ll run out of air before the cold kills us. But I could be wrong about asphyxiating before freezing to death.

See also https://science.nasa.gov/universe/what-happens-when-something-gets-too-close-to-a-black-hole/

Edit: as others on here have noted, our star isn’t big enough to become a black hole. The above assumes “But what if it did?”